Footwear

1. A footwear, comprising:

an outsole portion having a portion to be in contact with the ground; and

an upper portion having a portion crossing over instep of foot, the upper portion being attachable to and detachable from the outsole portion; wherein

a plurality of insertion pieces made of a material having elasticity is formed on a periphery of the upper portion,

a recess is formed on a center of an upper surface of the outsole portion,

insertion holes are formed on the outsole portion, the insertion holes being directed from an outer periphery of the outsole portion to the recess located at the center,

a groove is formed between each of the insertion holes so that a joint portion connecting each of the insertion pieces is fitted into the groove when the upper portion is attached to the outsole portion, the groove being directed from the outer periphery to an inner side of the outsole portion, and

the upper portion is attachable to the outsole portion by inserting the insertion pieces into the insertion holes in a direction toward the recess located at the center.

2. The footwear according to claim 1 , wherein

a locking hole is formed on each of the insertion pieces, and

locking protrusions are formed at a bottom of the recess formed on the center of the upper surface of the outsole portion, the locking protrusions being located at a position enabling to lock the locking hole in a state that each of the insertion pieces is penetrated through the insertion holes.

3. The footwear according to claim 1 , further comprising

an insole portion attached to the upper surface of the outsole portion, wherein

a locking hole is formed on each of the insertion pieces,

a fitting hole is formed at a bottom of the recess formed on the center of the upper surface of the outsole portion, the fitting hole being located at a position to be overlapped with the locking hole in a state that each of the insertion pieces is penetrated through the insertion holes, and

a fitting protrusion is formed on the insole portion, the fitting portion being located at a position enabling to pass through the locking hole and to fit with the fitting hole in a state that the upper portion and the insole portion are attached to the outsole portion.

4. The footwear according to claim 1 , wherein

a locking claw or a locking constriction is formed on a tip of each of the insertion pieces, and

a lock receiving portion is formed at a bottom of the recess formed on the center of the upper surface of the outsole portion, the lock receiving portion being located at a position enabling to lock the locking claw or the locking constriction in a state that each of the insertion pieces is penetrated through the insertion holes.

5. The footwear according to claim 1 , further comprising

an insole portion attached to the upper surface of the outsole portion, wherein

a locking claw or a locking constriction is formed on a tip of each of the insertion pieces, and

a lock receiving portion is formed on the insole portion, the lock receiving portion being located at a position enabling to lock the locking claw or the locking constriction in a state that the upper portion and the insole portion are attached to the outsole portion.

6. The footwear according to claim 1 , wherein

a locking claw is formed on a tip of each of the insertion pieces, and

each of the insertion pieces has a shape to be contracted during when the insertion pieces are inserted into the insertion holes and to be expanded after penetrated through the insertion holes so that the insertion holes function as a lock receiving portion.

7. The footwear according to claim 2 , wherein

a dimension of each of the insertion holes is specified so that the insertion pieces can be inserted into the insertion holes after when the insertion pieces becomes smaller in width by being in contacted with the insertion holes and pushed by the insertion holes from both lateral ends of the insertion pieces to shrink the locking hole.

8. The footwear according to claim 2 , wherein

each of the insertion pieces is sharp-edged at a front end and tongue-shaped, and

the locking hole is formed in a long shape longitudinally along a direction of inserting the insertion pieces.

9. The footwear according to claim 2 , wherein

each of the insertion pieces is sharp-edged at a front end and tongue-shaped, and

the locking hole is sharp-edged at a front end and/or a rear end in a direction of inserting the insertion pieces.

10. The footwear according to claim 2 , wherein

each of the locking protrusions or the lock receiving portion is inclined upward in a slope shape toward a front side in a direction of inserting the insertion pieces.

11. The footwear according to claim 3 , wherein

the fitting protrusion and the fitting hole are formed in a locking shape.

12. A footwear, comprising:

an outsole portion having a portion to be in contact with the ground; and

an upper portion having a portion crossing over instep of foot, the upper portion being attachable to and detachable from the outsole portion; wherein

a plurality of insertion pieces made of a material having elasticity is formed on a periphery of the upper portion,

a recess is formed on a center of a lower surface of the outsole portion,

insertion holes are formed on the outsole portion, the insertion holes being directed from an outer periphery of the outsole portion to the recess located at the center,

a groove is formed between each of the insertion holes so that a joint portion connecting each of the insertion pieces is fitted into the groove when the upper portion is attached to the outsole portion, the groove being directed from the outer periphery to an inner side of the outsole portion, and

the upper portion is attachable to the outsole portion by inserting the insertion pieces into the insertion holes in a direction toward the recess located at the center.